There are plenty of moments throughout Demon Slayer between Tanjirou and Nezuko that prove their sibling bond is unbreakable. Growing up as the oldest children of a large family, the two were surrounded by love their entire lives. When Kibutsuji Muzan slaughters their mother and siblings and turns Nezuko into a demon, their lives are upended forever, and they must rely on each other more than ever.
https://screenrant.com/best-demon-slayer-tanjirou-nezuko-moments/